Carboxyl-functionalized multifunctional red-emitting carbon quantum dots as an ideal biomaterial.

Carbon quantum dots (CQDs) have been developed into a popular nanomaterial due to their abundant surface state, good biocompatibility, and excellent antimicrobial properties. However, CQDs with multiple functions, such as being red-emitting, having good antibacterial activity, and having excellent pH sensitivity, have rarely been reported. In this work, red-emitting CQDs (R-CQDs) with excellent optical properties and antimicrobial activity were prepared by a simple green hydrothermal method. In antimicrobial applications, the R-CQDs featured good antibacterial activity due to the generation of reactive oxygen species, indicating excellent photodynamic antimicrobial ability. In addition, the R-CQDs showed fine pH sensitivity, giving them potential as pH sensors to monitor the pH of wounds in real time. The promising potential application of R-CQDs for cell imaging was also demonstrated. In summary, we offer R-CQDs with good antibacterial and pH sensitivity as a potential nanomaterial for pH and antimicrobial monitoring of wounds, shedding light on the biomedical field.